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Salvinia molesta (aquatic plant, herb)  |
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Management Information
Location Specific Management InformationAustralia
A biological control programme for S. molesta was undertaken simultaneously with programmes for the other aquatic invaders Eichhornia crassipes, Pistia stratiodes and Hydrilla verticillata, to avoid the increase of other invasive species as one was controlled. Australia
Preventative measures: Legislation in Australia prohibits the importation of all species of the genus Salvinia (under commonwealth quarantine legislation). The 2000 National strategic plan for salvinia identified prevention strategies (including public education) as the most effective way of managing any invasive weed. The prevention of the trade of salvinia is targeted as an area of improvement, with possible strategies including an enquiry into the effectiveness of the current legislation and an attempt to limit the demand for S. molesta by encouraging the aquatic community to use similar (but non-weedy) aquatic plant species as alternatives to salvinia. To minimise the impact of salvinia in areas where it is already established integrated biological control was emphasised as the best strategy. In addition, local agencies should be encouraged to close or restrict assess to infested waterways to limit spread of the weed. Biological: The first ever use of C. salviniae to control S. molesta occured in Lake Moondarra (northern Australia) in 1980. Within a year the 200 ha infestation had been destroyed. The average time needed to control an infestation in Australia using C. salviniae is estimated to be between 2 and 4 years (Room et al. 1981; Forno, 1985; Thomas and Room, 1986, in Room and Fernando, 1992). Queensland local government authorities keep breeding tanks of C. salviniae to assist with infestations in the region. The Queensland local government has produced a facts pest series sheet for salvinia outlining ways in which the public can limit the spread of the weed. Brisbane City Council (BBC) and Redlands Shire Council maintain pools for breeding of C. salviniae. The Far North Coast County Council (NSW) has three collection sites. A pyralid moth (Samea multiplicalis) has been trialed as a biological control agent in Lake Julius (Queensland) but did not effectively control the weed (PIER, 2003). Physical: Manual removal of the weed is only carried out to alleviate water blockages in the short-term, and not as a permenant solution. This is because re-infestation is certain and the cost of manual control is high. Habitat modification is a useful strategy in modified areas or areas in which the use of herbicides is unacceptable. It is not appropriate for environmentally unique areas. Damns, man-made lakes, canals and other water bodies can be drained (or the water level reduced) to strand and dry out the salvinia. Botswana
The role of contaminated equiptment associated with water activities in encouraging the spread of salvinia has been recognised in Botswana and strict inspection of boats and tailers has been instigated (Howard and Harley, 1998). C. salviniae has also been used successfully to control S. molesta in the country. Colleton County (United States (USA))
Eradication commenced several months after the detection of Salvinia molesta. Hand removal from the pond was followed by herbicide application. Fiji
The weevil C. salviniae has been used successfully to control S. molesta in Fiji. Kakadu National Park (Australia)
S. molesta had been eradicated from a total of five creeks and river systems by the early 1980s. All existing infestations are currently under adequate control by C. salviniae. Monitoring of the Cyrtobagous/Salvinia system with an emphasis on integrated biological and chemical control is being undertaken at Mission Hole on the Daly River, and in Kakadu National Park (ARMCANZ, 2000). Recommended measures for longterm control of salvinia on the Magela floodplain involve the continued use of weevils in conjunction with herbicides, restricted access, and mechanical harvesting (Finlayson 1994, Storrs & Julien 1996, in Gardner and Finlayson, 2002).Integrated management: The Australian Nature Conservation Agency (ANCA) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) are participating in an integrated management project to control S. molesta in the Kakadu National Park, as outlined below: Biological: Initial release of the beetle C. salviniae occured in 1983. In the Magela creek system the weed continued to spread for several years and the weevil population did not expand. It was reported that control failed (despite being successful at nearby sites), due to high temperatures, which were hypothesised to negatively impact the beetle population (Miller and Wilson, 1989, in Room and Fernando, 1992). Since then studies have futhur characterised the climatic conditions that affect the growth and establishment of C. salviniae in this region. In general conditions unfavourable to the beetles are either (i) a late wet season followed by flooding, or (ii) a poor wet season (either absent or halted). In these cases the following additional control measures are implemented. An excessive build up of secondary vegetation on salvinia infestations (which prevent the sinking of salvinia mats heavily infested by beetles) may also lead to the need for additional control measures.
Chemical: Herbicide is applied by hand or via boats onto vegetation (AF100 is used against loose floating mats and hexazinone is used against compact mats).
Physical: Floating ropes anchored to the bank are used to reduce the spread of the weed due to water currents. Driving airboats over mats (heavily damaged and blackened by weevils) at the end of the dry season has improved sinking.
Cultural: Access is prevented to infested areas and activities associated with boating, fishing or motor vechicles are restricted. Displays of salvinia (immature and mature) are used to help the public and new staff identify the weed. Information displays aimed at those visiting the park are used to encourage the reporting of infestations to the appropriate authorities. Kenya
The weevil C. salviniae was released in May 1991 in Lake Naivasha and by mid-1995 the weed had become a rarity in most parts of the lake and fringing wetlands. Although water hyacinth (E. crassipes) has partly invaded areas previously inhabited by salvinia, it is not as well adapted to the environment of the lake, which contains dissolved salts and is exposed to low night temperatures. Malaysia
The weevil C. salviniae has been used successfully to control S. molesta. Namibia
The weevil C. salviniae has been used successfully to control S. molesta in this country (Room, 1986; 1990, in Room and Fernando, 1992) New South Wales (Australia)
Due to the difficulty of herbicide control (because of the issues of water contamination and effectiveness), more people are experimenting with biological and physical control methods. Biological control produced reasonable results north of Coffs Harbour. In New South Wales it is estimated that C. salvinae saved A$100 000 (US$77 000) worth of chemical and physical control per annum. At the moment manual control in most situations is difficult, costly and inefficient, requiring on-going follow-ups. Despite all efforts salvinia is still a common plant in the aquarium industry. It still can be found in nurseries and aquarium shops, particularly in the larger urban centres. New Zealand
Champion and Clayton (2000; 2001a, in Champion, Clayton and Rowe, 2002) designed an aquatic plant weed risk assessment model for New Zealand based on invasiveness level, potential distribution and potential impact; using this model S. molesta was rated 57 (or the 16th highest priority of a total of 36 species rated). The Biosecurity Act (1993) allows for the development of Pest Management Strategies (PMS) at either a central government level or a regional level. These are known as National Pest Management Strategies (NPMS) and Regional Pest Management Strategies (RPMS), respectively. Despite the apparent moderate rating of S. molesta it is among only five weeds nominated by MAF for the development of an NPMS. Two other aquatic weeds have also been targeted by MAF: water hyacinth and water lettuce (Pistia stratiotes). Papua New Guinea
The weevil C. salviniae has been used successfully to control S. molesta in Papua New Guinea; although the impact of salvinia was catastrophic, it now only causes occasional localised problems. The average time needed to control an infestation of S. molesta using C. salviniae is estimated to be between 1 and 2 years in Papua New Guinea (Pieterse et al, 2003; Thomas and Room, 1986, in Room and Fernando, 1992). Philippines
The weevil C. salviniae has been used successfully to control S. molesta. Queensland (Australia)
Integrated management: Priority for control in Queensland is in the Murray-Darling and Lake Eyre catchment since these areas currently contain small infestations (which have the potential to expand considerably). Isolated infestations (such as in the Dawson River and in Banana Shire) should be controlled to prevent spread into salvinia free systems. Brisbane City Council keeps a population of salvinia in order to raise C. salviniae for the annual control of infestations. Some northern shires also carry out dispersal of this agent, although most infestations are flushed into the sea by annual floods. Total eradication of salvinia from Queensland is not practical or feasible. A reduction in the rate of spread of salvia is, however, realistic. Enforced control (including biological, chemical and physical removal) is required for isolated infestations up-stream of clean water bodies and in the Murray-Darling catchment. Preventative measures: The Queensland Government recently published a salvinia facts sheet (in a pest series) to educate the public on the best ways of controlling and limiting the spread of the weed. It recommends that C. salviniae be released in the spring in warm sunny positions with a high density of salvinia not affected by drops in the water level (which would leave the plants stranded). Chemical: Herbicides registered for use against the weed are listed and include: AF-100 (calcium dodecylbenzene sulphonate, orange oil with surfactant (not for use in natural waterbodies) and diquat (Vegetrol, Watrol or Reglone®). Senegal River
Integrated management: In early 2000 the IUCN held meetings with the Djoudj National Bird Sanctuary scientific committee and relevant experts (including a co-ordinator from the Royal Tropical Institute in Amsterdam, Holland). Following the advice of these meetings the Government of Senegal put in place a crisis committee to direct the implementation of integrated control of S. molesta (IUCN, 2002). Strategies of control implemented are outlined below: Physical: Between June and July (2000) an expensive and labour intensive intervention was undertaken by the army in Senegal to remove the weed manually. Nets were often torn due to the huge biomasses involved and within two months the weeds had re-invaded the cleared waterbodies. Manual removal was mostly abandoned but proved useful for particularly sensitive areas were rapid intervention was required. Floating barriers and tight-mesh nets were also erected to prevent the spread of the weed (IUCN, 2002). S. molesta infestations in the Senegal River Delta area were cleared up within a year and a half at a cost of less than US$1000. Biological: Effective control of S. molesta was obtained by means of the weevil C. salviniae. In 2000 weevils were obtained from the Plant Protection Research Institute in Pretoria, South Africa; two groups of 300 weevils were released on infestations in the Senegal River (in a site in Mauritania in May and in a site in Senegal in June). Transportation costs were funded by the local people in Mauritania and by the IUCN in Senegal. In Senegal the weevils failed to become established (due to stong winds) but in Mauritania the weevils, which were reared in plastic containers and released at sites protected from water currents and wind, became established and began spreading. In 2001, under the project "Policy research to identify conditions for optimal functioning of the Senegal River ecosystem in Mali, Mauritania and Senegal" (co-ordinated by the Royal Tropical Institute and funded by the EU), 1200 more weevils were shipped to Senegal, reared at the biological station in the Djoudj National Park, monitored by specialists and released between April and June. Detailed monitoring of the dispersal of C. salviniae (between November and December) suggested that biological control had been effective and by April 2002 S. molesta was no longer a problem in the National Parks or in the Delta area. An FAO financed project also released S. molesta into the Senegal river in late 2001 (IUCN, 2002; Pieterse et al, 2003). South Africa
The weevil C. salviniae has been used successfully to control S. molesta (Pieterse et al, 2003). South Australia (Australia)
Under the Animal and Plant Control (Agricultural Protection and Other Purposes) Act (1986) salvinia must be destroyed wherever it is found. Salvinia is still grown in backyard pools and aquaria but is confiscated if it comes to the attention of the APCC or local Board officers. Retailers can be prevented from selling or giving away salvinia. South India (India)
In 1982 C. salviniae was released in Bangalore and Trichur and successfully controlled S. molesta (Singh, 1989, in Lancer et al. 2001). The average time needed to control an infestation of S. molesta using C. salviniae is estimated to be between 1 and 1.5 years in southern India (Joy et al. 1985; Jayanth, 1987, in Room and Fernando, 1992). Sri Lanka
Manual removal and herbicide treatment in the early 1950’s proved to have limited success in controlling S. molesta. Biological: An extensive biological project carried out between 1982 and 1990 resulted in an estimated 99% of the 130 treated S. molesta infestations being partially destroyed and 80% being completely destroyed. The average time needed to control infestations in Sri Lanka (using C. salviniae) was estimated to be between 1 and 2 years and a cost:benefit analysis estimated a return of 53:1 in cash and 1673:1 in labour. In late 1986 adult C. salviniae were collected from Australia and tested for host-specificity in Sri Lanka. After proving to be host-specific, they were placed in floating cages on two infestations of S. molesta. Plants were treated with fertiliser (because increased nitrogen levels stimulate C. salviniae reproduction). Between five and ten months after the intial translocation, the beetle populations had reached sufficient sizes to warrent dispersal. Beetles (in groups of 200) were translocated to nine infestation sites. The beetles were placed on weeds that were enclosed in floating bamboo frames, anchored to the ground, to allow weekly monitoring. In late 1987 further dispersal of the beetles occurred. By mid 1988 the beetles were dispersed to over 130 sites. From early 1988 the public were informed (via television, newspapers and radio) of beetle locations to encourage dispersal of beetles to infestations of S. molesta. Extensive monitoring between 1986 and 1990 revealed that of the 99 sites surveyed 77 had been completely destroyed, 21 had been partially destroyed and only one had remained unaffected by the beetles. The failure at was thought to be due to the large amount of vegetation growing on and among the weed. Beetle population growth and weed reduction generally followed a similar pattern: initial slow dispersal, followed by several months of increasing speed of dispersal and population growth and finally (over a matter of only a few days) a sudden browning and senescence of the salvinia mats. Mats would sink leaving only a few isolated small plants (interspersed among the emergent vegetation in the shallows). Nitrogen content had an impact on the time it took to control an infestation. Natural migration of the beetle was evident as the beetle was found to be present in sites where it had not been released. In fact, the beetle population in Mahawewa, which crashed temporarily (possibly due to unusually high temperatures), was naturally revived. A re-infestation of S. molesta in Thinipitiyawewa (following its eradication by beetles) was subsequently controlled by a beetle population that had become naturally re-established. Tasmania (Australia)
Salvinia auriculata and S. molesta are declared weeds under the Weed Management Act (1999). These plants are prohibited entry into Tasmania, and must not be sold or distributed in Tasmania. Tengwe Tobacco Commercial Farming area (Zimbabwe)
Mechanical, physical and chemical control methods to contain salvinia in the Tengwe dams have had limited success (P.W. Dawson, pers. comm., in Chikwenhere and Keswani, 1997). Physical: In 1989 about 400 days of manual labour were utilised to clear the weed (at cost of approximately US$ 1,700). This temporarily and partially cleared waterways but reinfestation was apparent within three weeks. Due to this it was virtually impossible to achieve sustainable control by manual removal. Floating barriers were erected in both dams to improve assessibility to the water (for livestock). This cost approximately US$ 900 (including the costs of labour the burning of the cleared weed). Chemical: In 1990 a helicopter was used to aerially spray the infestations with glyphosate (at a cost of approximately US$ 6,400). This achieved satisfactory control but, again, reinfestation was apparent within three weeks. Biological: Between 1992 and 1995 the weevil C. salviniae was used to control S. molesta. The effectiveness of C. salviniae was evident within four months. Before the control program salvinia had covered 90% of the dams; after two years of control using C. salviniae more than 99% of the dams were cleared. Commercially important fish and indigenous species that had previously been lost were able to recover. Water quality increased and pesticide use decreased. The biological control details are summarised as follows:
In May 1992 a starter colony of 550 adult weevils (C. salviniae) was imported from the Department of Water Affairs of Botswana and 300 were released immediately into the two dams. The rest were cultured in ten containers (approximately 50 cm wide and 40 cm deep) and were incubated at about 26°C. The containers were replenished with water, plant nutrients and fresh S. molesta regularly. After six months (between November 1992 and February 1993) approximately 500 infested plants (containing more than 3500 weevils) were distributed between the dams. United States (USA)
S. molesta is cultivated in at least sixteen states in the USA. Cultivation refers to commercial nurseries, botanical gardens and home ponds. Nursery sales have been documented in twelve states. Florida hosts an early record of S. molesta in the aquatic plant and water-garden market, during 1983 (Nelson 1994). By the early 1990s it was observed at nurseries in other southern states. Victoria (Australia)
Salvinia is one of 14 weeds prohibited in Victoria. It is to be eradicated from the state if possible. Western Australia (Australia)
Salvinia is declared P1, P2 (eradication) under the Agriculture and Related Resources Protection Act (1976) for the whole state. In many cases infestations are cleaned up by community groups or local government. Almost all infestations are the result of the dumping of salvinia originating from garden ponds, which suggests that management should be targeted at educating pond and aquarium owners about the risks associated with dumping salvinia into the environment. Zambia
The weevil C. salviniae has been used successfully to control S. molesta. Zimbabwe
Preventative measures: The movement of boats to and from Lake Kariba may have been responsible for the spread of salvinia into inland waterbodies in Zimbabwe. If boat movement to and from Lake Kariba continues to proceed unchecked it is thought that most water bodies will eventually be infested with the weed. Appropriate preventative strategies include restricting access to heavily infested areas, educating people who use the waterways about the importance of cleaning boats and enforcing quarantine procedures.Biological: Paulinia acuminata, an aquatic grasshopper introduced into Lake Kariba in the 1960s was believed to keep the salvinia population in check.In Zimbabwe the economic advantage of using C. salvinae was estimated at a ratio of 1:10.6 over a four year period. The first year of biological control came to approximatley US$ 500, whereas by the third year costs had been reduced to approximately US$ 90.
Management Resources/Links
2. Bowcher, A. and Lee, T. 2003. Integrated Weed Management: Salvinia (fact sheet). CRC for Australian Weed Management.
Summary: Integrating management options into a viable management plan in Kakadu National Park. 5. Champion, P.D.; Clayton, J.S. 2001. Border control for potential aquatic weeds. Stage 2. Weed risk assessment. Science for Conservation 185. 30 p.
Summary: This report is the second stage in the development of a Border Control Programme for aquatic plants that have the potential to become ecological weeds in New Zealand. Importers and traders in aquatic plants were surveyed to identify the plant species known or likely to be present in New Zealand. The Aquatic Plant Weed Risk Assessment Model was used to help assess the level of risk posed by these species. The report presents evidence of the various entry pathways and considers the impact that new invasive aquatic weed species may have on vulnerable native aquatic species and communities.
Available from: http://www.doc.govt.nz/upload/documents/science-and-technical/SFC185.pdf [Accessed 13 June 2007] 6. Chikwenhere, G.P. and Keswani, C.L. 1997. Economics of Biological Control of Kariba Weed (Salvinia molesta Mitchell) at Tengwe in North-western Zimbabwe - a Case Study, International Journal of Pest Management 43(2): 109 - 112.
Summary: A summary on the use of Cyrtobagous salviniae as a biological control agent in heavily infested lake in Zimbabwe previously used for breeding fish (with an emphasis on cost:benefit analysis). 7. Dye, J.M. and Heinz, K.M. Undated Biological control of Salvinia species. A&M University (Department of Entomology): Texas.
Summary: Salvinia Biocontrol poster 9. International Union for the Conservation of Nature (IUCN). 2002. Note on the Control of Salvinia Molesta in Djoudj National Bird Sanctuary (Senegal).
Summary: Outline of the proceedings of the IUCN and associated organisations that initiated a biological control project (using Cyrtobagous salviniae) to manage salvinia in the Senegal River Delta area. 14. Lancer, L., Krake, K., Brabben, T., Plantey, J. and Malano, H. 2002. Aquatic Weeds and Their Management. Working Group on Development and Management of Irrigation Systems (WG-DMIS): International Commission on Irrigation and Drainage. 15. Land Protection. 2004. Salvinia: Salvinia Species, (facts pest series). The State of Queensland Department of Natural Resources and Mines.
Summary: Information dealing with the control of Salvinia molesta in Queensland with information on how the general public can reduce the spread of salvinia (by biological or chemical control). Includes a list of herbicides registered for use on salvinia. 17. May, Michael, Cristina Grosso, and Josh Collins., 2003. Giant salvinia. Practical Guidebook for the Identification and Control of Invasive Aquatic and Wetland Plants in the San Francisco Bay-Delta Region San Francisco Estuary Institute Oakland, California
Summary: Information on description, economic importance, distribution, habitat, history, growth, and impacts and management of species.
Available from:
http://www.sfei.org/nis/salvinia.html [Accessed 22 June 2005].
The Guidebook is available from: http://www.sfei.org/nis/ 19. National Pest Plant Accord, 2001. Biosecurity New Zealand.
Summary: The National Pest Plant Accord is a cooperative agreement between regional councils and government departments with biosecurity responsibilities. Under the accord, regional councils will undertake surveillance to prevent the commercial sale and/or distribution of an agreed list of pest plants.
Available from: http://www.biosecurity.govt.nz/pests-diseases/plants/accord.htm [Accessed 11 August 2005] 22. Pieterse, A.H., Kettunen, M., Diouf, S., Ndao, I., Sarr, K., Tarvainen, A., Kloff, S. and Hellsten, S. 2003. Effective biological control of Salvinia molesta in the Senegal River by Means of the Weevil Cyrtobagous salviniae, Ambio 32 (7): 458 - 462.
Summary: History of the spread, impacts, biological control (and subsequent monitoring) of S. molesta in the Senegal River. 24. Room, P.M. and Fernando, I.V.S. 1992. Weed Invasions Countered by Biological Control: Salvinia molesta and Eichhornia crassipes in Sri Lanka, Aquatic Botany 42: 99 - 107.
Summary: This paper gives an excellent outline of the biological control of S. molesta in Sri Lanka between 1982 and 1990, including a history of the weed in the country, an overview of the release and distribution of the weevil (Cyrtobagous salviniae) and an summary of the results and most interesting findings. Also mentions the performance of Neochetina eichhorniae as a biological control agent for water hyacinth (Eichhornia crassipes). 25. Room, P.M., 1990, Ecology & Evolution, 5:77. Doeleman, J.A., ‘Biological Control of Salvinia molesta in Sri Lanka; an assessment of costs and benefits’, Australian Centre for International Agricultural Research, Technical Report 12.
Summary: Management information on Salvinia molesta. 28. Swearingen, J., Reshetiloff, K., Slattery, B. and Zwicker, S. 2002. Plant Invaders of Mid-Atlantic Natural Areas: Giant Salvinia - Salvinia molesta. National Park Service and U.S. Fish & Wildlife Service
Summary: Online book that includes information on origin, spread, distribution, description, methods of disposal, and look-alikes. 30. Van Wilgen, B.W., Richardson, D.M., Le Maitre, D.C., Marais, C. and Magadlela, D. 2001. The Economic Consequences of Alien Plant Invasions: Examples of Impacts and Approaches to Sustainable Management in South Africa, Environment, Development and Sustainability 3: 145 - 168.
Summary: Overview of the consequences of invasive weed species introduced into South Africa. Results Page: 1
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